Record retention is best looked at by your document types, life cycle of your product(s), importance of the information and impact on your, and your customers', business. Also get your financial/legal people involved to help identify items that need to be kept for legal or tax purposes, etc.
If you have records that contain information that is transferred to another form, you may not have to keep them as long as some others. An example might be if you are keying information into your computer systems from forms filled in by hand. Maybe you only want to keep the hand-written records for one year (or less) and the computer record becomes your "official" record. Use your history of data entry accuracy to help you here.
Obviously, if you work in a sector where product life cycles are long and impact on safety is high, you may want to keep records a longer time. But you are not going to add any value by keeping your internal audit records for five years. A typical audit cycle is three years, why hang on to those records for 5, for example.
The problem that I have seen most often is that too many companies just say "we will keep the records for 5, 7, 10 or how many ever years." If you spend a little time up front and figure out how long you really need the records, you can reduce costs dramatically in record retention. 1) man-hours spent moving files to different locations as you run out of room. 2) Additional storage areas, new construction or remodeling. 3) Reduced number of filing cabinets/boxes, etc. 4) If you are really into the tree-hugging (I am) you can often times re-use the folders for items with a less-lengthy retention.
I hope this helps somewhat, I remember the first ISO system I did and record retention seemed like an overwhelming menace. Just look at things with the viewpoint of "How many times do I reference this after 1 year, after 3 years, after 7 years, etc. etc." It's kind of like cleaning out the closets or the utility shed!